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Object Creation
In object-oriented programming (OOP), the object lifetime (or life cycle) of an object is the time between an object's creation and its destruction. Rules for object lifetime vary significantly between languages, in some cases between implementations of a given language, and lifetime of a particular object may vary from one run of the program to another. In some cases, object lifetime coincides with variable lifetime of a variable with that object as value (both for static variables and automatic variables), but in general, object lifetime is not tied to the lifetime of any one variable. In many cases – and by default in many object-oriented languages, particularly those that use garbage collection (GC) – objects are allocated on the heap, and object lifetime is not determined by the lifetime of a given variable: the value of a variable holding an object actually corresponds to a ''reference'' to the object, not the object itself, and destruction of the variable just destr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object-oriented Programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of procedures (often known as ''methods''). A common feature of objects is that procedures (or methods) are attached to them and can access and modify the object's data fields. In this brand of OOP, there is usually a special name such as or used to refer to the current object. In OOP, computer programs are designed by making them out of objects that interact with one another. OOP languages are diverse, but the most popular ones are class-based, meaning that objects are instances of classes, which also determine their types. Many of the most widely used programming languages (such as C++, Java, Python, etc.) are multi-paradigm and they support object-oriented programming to a greater or lesser degree, typically in combination with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Local Variable
In computer science, a local variable is a variable that is given ''local scope''. A local variable reference in the function or block in which it is declared overrides the same variable name in the larger scope. In programming languages with only two levels of visibility, local variables are contrasted with global variables. On the other hand, many ALGOL-derived languages allow any number of nested levels of visibility, with private variables, functions, constants and types hidden within them, either by nested blocks or nested functions. Local variables are fundamental to procedural programming, and more generally modular programming: variables of local scope are used to avoid issues with side-effects that can occur with global variables. Scope Local variables may have a lexical or dynamic scope, though lexical (static) scoping is far more common. In lexical scoping (or lexical scope; also called static scoping or static scope), if a variable name's scope is a certain block, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subroutine
In computer programming, a function or subroutine is a sequence of program instructions that performs a specific task, packaged as a unit. This unit can then be used in programs wherever that particular task should be performed. Functions may be defined within programs, or separately in libraries that can be used by many programs. In different programming languages, a function may be called a routine, subprogram, subroutine, method, or procedure. Technically, these terms all have different definitions, and the nomenclature varies from language to language. The generic umbrella term ''callable unit'' is sometimes used. A function is often coded so that it can be started several times and from several places during one execution of the program, including from other functions, and then branch back (''return'') to the next instruction after the ''call'', once the function's task is done. The idea of a subroutine was initially conceived by John Mauchly during his work on EN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Name Resolution (programming Languages)
In programming languages, name resolution is the resolution of the tokens within program expressions to the intended program components. Overview Expressions in computer programs reference variables, data types, functions, classes, objects, libraries, packages and other entities by name. In that context, name resolution refers to the association of those not-necessarily-unique names with the intended program entities. The algorithms that determine what those identifiers refer to in specific contexts are part of the language definition. The complexity of these algorithms is influenced by the sophistication of the language. For example, name resolution in assembly language usually involves only a single simple table lookup, while name resolution in C++ is extremely complicated as it involves: * namespaces, which make it possible for an identifier to have different meanings depending on its associated namespace; * scopes, which make it possible for an identifier to have differen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Declaration (computer Programming)
In computer programming, a declaration is a language construct specifying identifier properties: it declares a word's (identifier's) meaning."A declaration specifies the interpretation and attributes of a set of identifiers. A ''definition'' of an identifier is a declaration for that identifier that: * for an object ariable or constant causes storage to be reserved for that object; * for a function, includes the function body; * for an enumeration constant, is the (only) declaration of the identifier; * for a typedef name, is the first (or only) declaration of the identifier." C11 specification, 6.7: Declarations, paragraph 5. Declarations are most commonly used for functions, variables, constants, and classes, but can also be used for other entities such as enumerations and type definitions. Beyond the name (the identifier itself) and the kind of entity (function, variable, etc.), declarations typically specify the data type (for variables and constants), or the type signat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initialization (programming)
In computer programming, initialization (or initialisation) is the assignment of an initial value for a data object or variable. The manner in which initialization is performed depends on the programming language, as well as the type, storage class, etc., of an object to be initialized. Programming constructs which perform initialization are typically called initializers and initializer lists. Initialization is distinct from (and preceded by) declaration, although the two can sometimes be conflated in practice. The complement of initialization is finalization, which is primarily used for objects, but not variables. Initialization is done either by statically embedding the value at compile time, or else by assignment at run time. A section of code that performs such initialization is generally known as "initialization code" and may include other, one-time-only, functions such as opening files; in object-oriented programming, initialization code may be part of a '' constructor'' (cla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object Pool
The object pool pattern is a software creational design pattern that uses a set of initialized objects kept ready to use – a "pool" – rather than allocating and destroying them on demand. A client of the pool will request an object from the pool and perform operations on the returned object. When the client has finished, it returns the object to the pool rather than destroying it; this can be done manually or automatically. Object pools are primarily used for performance: in some circumstances, object pools significantly improve performance. Object pools complicate object lifetime, as objects obtained from and returned to a pool are not actually created or destroyed at this time, and thus require care in implementation. Description When it is necessary to work with numerous objects that are particularly expensive to instantiate and each object is only needed for a short period of time, the performance of an entire application may be adversely affected. An object pool desi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escape Analysis
In compiler optimization, escape analysis is a method for determining the dynamic scope of pointers where in the program a pointer can be accessed. It is related to pointer analysis and shape analysis. When a variable (or an object) is allocated in a subroutine, a pointer to the variable can ''escape'' to other threads of execution, or to calling subroutines. If an implementation uses tail call optimization (usually required for functional languages), objects may also be seen as escaping to ''called'' subroutines. If a language supports first-class continuations (as do Scheme and Standard ML of New Jersey), portions of the call stack may also escape. If a subroutine allocates an object and returns a pointer to it, the object can be accessed from undetermined places in the program the pointer has "escaped". Pointers can also escape if they are stored in global variables or other data structures that, in turn, escape the current procedure. Escape analysis determines all the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compiler Optimization
In computing, an optimizing compiler is a compiler that tries to minimize or maximize some attributes of an executable computer program. Common requirements are to minimize a program's execution time, memory footprint, storage size, and power consumption (the last three being popular for portable computers). Compiler optimization is generally implemented using a sequence of ''optimizing transformations'', algorithms which take a program and transform it to produce a semantically equivalent output program that uses fewer resources or executes faster. It has been shown that some code optimization problems are NP-complete, or even undecidable. In practice, factors such as the programmer's willingness to wait for the compiler to complete its task place upper limits on the optimizations that a compiler might provide. Optimization is generally a very CPU- and memory-intensive process. In the past, computer memory limitations were also a major factor in limiting which optimizations co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object Resurrection
In object-oriented programming languages with garbage collection, object resurrection is when an object comes back to life during the process of object destruction, as a side effect of a finalizer being executed. Object resurrection causes a number of problems, particularly that the possibility of object resurrection – even if it does not occur – makes garbage collection significantly more complicated and slower, and is a major reason that finalizers are discouraged. Languages deal with object resurrection in various ways. In rare circumstances, object resurrection is used to implement certain design patterns, notably an object pool, while in other circumstances resurrection is an undesired bug caused by an error in finalizers, and in general resurrection is discouraged. Process Object resurrection occurs via the following process. First, an object becomes ''garbage'' when it is no longer reachable from the program, and may be collected (destroyed and deallocated). Then, du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reference Count
In computer science, reference counting is a programming technique of storing the number of references, pointers, or handles to a resource, such as an object, a block of memory, disk space, and others. In garbage collection algorithms, reference counts may be used to deallocate objects that are no longer needed. Advantages and disadvantages The main advantage of the reference counting over tracing garbage collection is that objects are reclaimed ''as soon as'' they can no longer be referenced, and in an incremental fashion, without long pauses for collection cycles and with clearly defined lifetime of every object. In real-time applications or systems with limited memory, this is important to maintain responsiveness. Reference counting is also among the simplest forms of memory management to implement. It also allows for effective management of non-memory resources such as operating system objects, which are often much scarcer than memory (tracing garbage collection systems u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manual Memory Management
In computer science, manual memory management refers to the usage of manual instructions by the programmer to identify and deallocate unused objects, or garbage. Up until the mid-1990s, the majority of programming languages used in industry supported manual memory management, though garbage collection has existed since 1959, when it was introduced with Lisp. Today, however, languages with garbage collection such as Java are increasingly popular and the languages Objective-C and Swift provide similar functionality through Automatic Reference Counting. The main manually managed languages still in widespread use today are C and C++ – see C dynamic memory allocation. Description Many programming languages use manual techniques to determine when to ''allocate'' a new object from the free store. C uses the malloc function; C++ and Java use the new operator; and many other languages (such as Python) allocate all objects from the free store. Determining when an object ought to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
